Pretty sure I know the answer, however I thought I'd get the official word from the Developer.
I decided hey I'm going to try something new, so I totally ignored Lani and I focused on Marla.
No more cuddle time, after a LONG while there was a scene where Lani gives advice, followed by meeting up at the library.
However nothing between "us" happens after that (I know it is mentioned that the conversation is "saved and meant to be used in a future update" however I'm still banned from cuddle time.
I know that if I did enough Lani stuff eventually we would come together, getting closer together.
But I was kinda hoping that Lani would suggest MC being included in cuddle time again for the sake of Marla. After all in the other games she mentions that she actually fell in love with MC before they even formed a party.
And that spending more time with the MC only deepened the feelings. Meaning there would be 2 ways to possibly end with with Lani, one of them the "Normal Way" and the other a simi more traditional way (talking, going on dates, taking walks, sleeping under the tree), might also be fun to see Lani acting more cat like in some cases (such as preferring to be naked outside, and being scolded for doing so by Luna. Maybe even using it to either embarrass or judge MC reaction to her body.
Though there is another scene you might want to change up, the dungeon fountain, after all of MC and Lani are actively having sex it makes no sense whatsoever to have her tell him to "Turn around and No Peeking" shouldn't they be in that fountain together at least playing...
If you did that then you could also have at least 4 versions of the fountain scene for the "succubus trial" depending on his relationships. If close to Marla but not Lani, if close to Lani and not Marla, if close to both and if not particularly involved with either. (Again just suggestions feel free to ignore them)
Honestly I wish I had the tools, knowledge and talent needed to make games like these, I always have so many ideas (some great, some good, some just barely passable) but none I'll ever be able to actualize due to lacking all of those things.